<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<input type="text" id="i1">
<input type="text" id="i2">
<input type="button"value="加" onclick="f(1)">
<input type="button"value="减" onclick="f(2)">
<input type="button"value="乘" onclick="f(3)">
<input type="button"value="除" onclick="f(4)">
<div>结果</div>

<script>
    let i1= document.querySelector("#i1");
    let i2= document.querySelector("#i2");
    let d=document.querySelector("div");
    function f(x) {
        if (isNaN(i1.value)||isNaN(i2.value)){
            d.innerText = "输入错误!";
            return;
        }
        switch (x){
            case 1: d.innerText = "结果:"+ (i1.value*1+i2.value*1);
                break;
            case 2: d.innerText = "结果:"+ (i1.value-i2.value);
                break;
            case 3: d.innerText = "结果:"+ (i1.value*i2.value);
                break;
            case 4: d.innerText = "结果:"+ (i1.value/i2.value);
                break;
        }

    }



</script>

</body>
</html>